Classic/Antique Car Repair: 51 Bentley Oil Pressure Gauge, oil pressure gauge, air pressure

Question
Hi,
I have a 1951 MKVI Bentley.  I purchased the car in parts and am slowly restoring it.  My question is the metal line that runs from the oil pressure gauge on the dash to the engine.  Is the line supposed to be filled with oil or is supposed to use air pressure to obtain a reading on the gauge?
Thanks


Answer
Graham:

Congratulations on buying a lovely, beautifully-driving, and very well-built automobile. I'm sure it will bring you much pleasure once the restoration is complete.

The oil pressure gauge is exactly that--for oil pressure. The line and gauge mechanism must be filled with oil for the gauge to function properly. If the mechanism is not reading properly, it must be bled at the joint and reassembled. Compressed air will not allow the gauge to operate properly.

--Paul